The electricity meters are used to measure a flow of electricity through a portion of an electricity network.
For example, an electricity meter may be used, in combination with a transformer and a converter, to measure a flow of electricity generated by a power station.
Furthermore, electricity meters, alone or in combination with a transformer and a converter, may also allow to measure the flow of electricity furnished by the electricity network to a consumption unit, e.g. a house, or a factory.
The electricity meters comprise a metering system powered by a powering system. The powering system allows to convert energy of the electricity network into a powering voltage.
The powering system is connected to the electricity network. If a blackout occurs, i.e. the electricity network no longer carries electricity to the consumption unit, or the power station stops generating electricity, the powering system inside the electricity meter is no longer supplied. The metering system is subsequently not powered either. However, since the flow of electricity to be measured is null during a blackout, the measurement of the electricity used up by the consumption unit, or generated at the power station, remains substantially correct.
The electricity meters may also comprise a clock and a non-rechargeable battery allowing to supply the clock in case a blackout occurs.
The power stations typically generate electricity as three phases and the electricity network may carry electricity from the power stations to the consumption units as three phases. However, the electricity network also furnishes electricity as a single phase to some consumption units, typically private houses. Some private houses are supplied by a three phases electricity network.
The electricity meters may hence comprise a single phase electricity meter allowing to measure the flow of electricity through a single phase, or a polyphase electricity meter allowing to measure the flow of electricity through a plurality of phases of the electricity network.
The current regulation requires that the polyphase electricity meters remain available during a predetermined lapse of time when the electricity network is partially disabled, i.e. a power failure occurs with one or two phases of a three phases electricity network.
The powering system of the polyphase electricity meters is hence connected to the three phases of the electricity network, since any one of the phases may be lost. The powering system has to be able to adapt to a loss of any one of the phases of the electricity network and is relatively complex.
There is a need for an electricity meter in which the metering system remains available when a power failure occurs in one or two phases if any of the electricity network.